In relation to some diseases patients must inject a medicament on a regular basis such as once weekly, once daily or even a plurality of times each day. In order to help patients overcome fear of needles, fully automatic injection devices have been developed with the aim of making the use of the injection device as simple and safe as possible. Such devices are typically designed such that a user shall position the injection device onto the injection site and activate the device. Such activation causes the device to insert a needle into the skin, eject a dose of the medicament and subsequently move the needle into a shielded position.
In injection devices, and in particular in auto injector devices with an integrated and shielded needle, it is desirable that the needle shield is locked after use. Some prior art devices include a locking feature where the locking feature is activated immediately after the needle shield is deflected for an injection whereafter, when the needle shield is extended into its shielding position, the lock is effectuated. This is sometimes a disadvantage due to the nature of auto injectors where a powerful pre-tensioned spring is released when the device is activated. Some patients may become surprised by the activation sound and/or reaction force and removes the device from the skin. In injectors where the needle shield locks when the device is prematurely removed from the skin the patient is unable to receive the intended dose.
WO 2012/137803 discloses an autoinjector wherein a needle protector is locked in a position shielding a needle but only after a dose has been finalised and the plunger has reached a final position. However, the disclosed device is associated with drawbacks having regard to movement of the protector which may tend to become jammed during extraction of the protector relative to the housing. Also, the robustness of the locking mechanism of the needle protector is not optimal. Furthermore, the locking of the protector occurs via further components making device unnecessary complex.
Having regard to the above-identified prior art devices, it is an object of the present invention to provide an injection device that is improved having regard to locking of the needle shield subsequent to performing an injection.
Yet additional further objects of the invention are to provide measures for obtaining devices having a superior performance and, at the same time, enabling manufacture at a reduced cost.